Poly[{μ10-[(phosphonomethyl)iminodimethylene]diphosphonato}dithallium(I)]

The title compound, [Tl2(C3H10NO9P3)]n, a TlI organic–inorganic hybrid complex, was synthesized by the reaction of nitrilotris(methylenephosphonic acid) with thallium(I) nitrate. There are two types of Tl+ ions in the complex, with coordination numbers of eight and seven and with stereochemically active and inactive lone-pair electrons, respectively. In the crystal, the doubly deprotonated ligands form two-dimensional hydrogen-bonded layers through O—H⋯O hydrogen bonds. The NH group is involved in a trifurcated intramolecular hydrogen bond. Coordination of the phosphonate ligands to the Tl+ ions creates a three-dimensional structure.

The title compound, [Tl 2 (C 3 H 10 NO 9 P 3 )] n , a Tl I organicinorganic hybrid complex, was synthesized by the reaction of nitrilotris(methylenephosphonic acid) with thallium(I) nitrate. There are two types of Tl + ions in the complex, with coordination numbers of eight and seven and with stereochemically active and inactive lone-pair electrons, respectively. In the crystal, the doubly deprotonated ligands form two-dimensional hydrogen-bonded layers through O-HÁ Á ÁO hydrogen bonds. The NH group is involved in a trifurcated intramolecular hydrogen bond. Coordination of the phosphonate ligands to the Tl + ions creates a three-dimensional structure.

Related literature
For related metal phosphonate complexes of the same ligand, see: Sharma et al. (2001).
In the structure of the title compound, synthesized by the reaction of the same ligand with thallium(I) nitrate, the nitrilotris(methylenephosphonate) (H4L 2-) group is doublely deprotonated and two different environments for the Thallium atoms are observed, as shown in Figs. 1 and 2. Eight O-atoms of five H4L 2phosphonate ligands are coordinated to the Tl1 ion ( Fig. 1), while seven oxygen atoms of five H4L 2phosphonate ligands are coordinated to the Tl2 ion (Fig. 2).
The conformation of the doublely deprotonated nitrilotris(methylenephosphonate) ligand is illustrated in Fig. 3. The hydrogen atoms on atoms O1 and O2 are positionally disordered with relative occupancies of 0.5:0.5. Each H4L 2dianion links to five Tl1 and five Tl2 ions (Fig. 4).
The doublely deprotonated H4L 2ligand forms two-dimensional hydrogen bonded layers via O-H···O hydrogen bonds involving hydroxyl groups O1, O2, O6 and O7 (Table 1 and Fig. 5). Atoms O3, O5 and O8 do not contribute in this type of hydrogen bond, rather they coordinate only to the Tl + ions. The NH group is involved in a 4-centre trifurcated intramolecular hydrogen bond with O-atoms O3, O5 and O8 (Table 1). Coordination of the ligand to the metal ions in the interlayer space creates a three-dimensional structure (Fig. 6).

Refinement
The NH and OH H-atoms were located in a difference electron-density map and were refined with distance restraints: O-H = 0.82 (2) and N-H = 0.86 (2) Å, with U iso (H) = 1.2U eq (N,O). The C-bound H atoms were positioned geometrically and refined using a riding model: C-H = 0.99 Å, with U iso (H) = 1.2 times U eq (C).